11.6. The Most Common Words¶

Coming back to our running example of the text from Romeo and Juliet Act 2, Scene 2, we can write a program using last section’s technique to print the ten most common words in the text as follows:

The first part of the program reads the file and creates/fills in the dictionary that maps each word to the amount of times it appears in the document. For this program, instead of simply printing out counts and ending the program, we construct a list of (val, key) tuples and then sort the list in reverse order.

Since the value is first, it will be used for the comparisons. If there is more than one tuple with the same value, it will look at the second element (the key), so tuples whose values are equal will be further sorted in reverse alphabetical order of the key.

At the end, we write a nice for loop which does a multiple assignment iteration and prints out the ten most common words by iterating through a slice of the list (lst[:10]).

Now, the output finally looks like what we want for our word frequency analysis.

i
and
romeo
to
the
thou
juliet
that
my
thee

The fact that this complex data parsing and analysis can be done with an easy-to-understand Python program is one reason why Python is a good choice as a language for exploring information.

11-9-2: Which of the following correctly uses the slice operator to grab the first 5 items of a list ‘lst’? Select all that apply.

lst[1:5]
Incorrect! Remember, list indices start at 0, not 1. Try again.
lst[:5]
Correct! This line of code slices list lst from its first value to its fifth value.
lst[0:4]
Incorrect! The slice operator stops at the index before the value after the colon. Try again.
lst[:4]
Incorrect! The slice operator stops at the index before the value after the colon. Try again.

11-9-3: How will the following code be sorted once this code is run?

weather = {'Reykjavik': 60, 'Buenos Aires': 55, 'Cairo': 96, 'Berlin': 89, 'Caloocan': 78}
sorted_weather = weather.sort()

First city name (alphabetically), then temperature (lowest to highest)
Incorrect! Remember, some methods can only be used on specific data types. Try again.
First temperature (highest to lowest), then city name(alphabetically)
Incorrect! Remember, some methods can only be used on specific data types. Try again.
First city name (alphabetically), then temperature (highest to lowest)
Incorrect! Remember, some methods can only be used on specific data types. Try again.
First temperature (lowest to highest), then city name (alphabetically)
Incorrect! Remember, some methods can only be used on specific data types. Try again.
An error will occur
Correct! The sort() method cannot be used on dictionaries. Instead, add the data from the dictionary to a list first.

Construct a block of code that uses tuples to keep track of the word count in the file ‘heineken.txt’. Then, print out the 10 most frequently appearing words preceded by how many times they appear.

        counter = {}
list_of_tuples = []
---
with open("heineken.txt", "r") as filename:
---
    lines = filename.readlines()
---
for line in lines:
---
    for word in line.split():
---
              for word in lines.split(): #paired
---
                  counter[word] = counter.get(word, 0) + 1
---
sorted_counts = sorted(counter.items(), key = lambda t: t[1], reverse = True)
---
sorted_counts = sorted(counter.items(), key = lambda t: t[1]) #paired
---
for t in sorted_counts[:10]:
---
    print(t)

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11.6. The Most Common Words¶